class GraphUtils
  def GraphUtils.get_test_graph
    # can't use neither the builder pattern nor a fixture-similar routine, 
    # because it's cyclic
    a = GraphNode.new("a")
    b = GraphNode.new("b")
    c = GraphNode.new("c")
    d = GraphNode.new("d")
    e = GraphNode.new("e")
    f = GraphNode.new("f")

    a.add_node(e, 5)
    a.add_node(f, 12)

    b.add_node(a, 15)
    b.add_node(c, 9)

    c.add_node(d, 5)

    d.add_node(b, 2)

    e.add_node(c, 10)
    e.add_node(f, 4)

    f.add_node(c, 17)
    f.add_node(d, 20)
    
    [a, b, c, d, e, f]
  end
end
